The present invention relates to an apparatus for controlling a vehicular transmission, and more particularly to an apparatus for controlling a transmission actuator associated with a transmission having a synchromesh.
There have been developed in recent years electronically controlled automatic vehicular transmissions employing microcomputers.
Transmission actuators for actuating such automatic transmissions are generally hydraulically operated actuators.
Where a hydraulic transmission actuator is employed, a hydraulic pressure generating device is required to supply a hydraulic pressure for operating the hydraulic transmission actuator. There are also required a hydraulic circuit for connecting the hydraulic pressure generating device and the actuator, and a control valve and other components for controlling the hydraulic pressure to be supplied to the actuator. The overall transmission actuator system is large in size, heavy in weight, and costly to manufacture.
One transmission actuator proposed to eliminate the aforesaid problems employs an electric motor.
A transmission actuator employing an electric motor to solve the above problems is disclosed in Japanese Patent Publication No. 61-45093, for example.
The disclosed transmission actuator includes a movable contact attached to a gear drivable by the motor, a pair of fixed contacts for contacting the movable contact, a first driver circuit connected to one of the fixed contacts for rotating the motor clockwise in response to a clockwise rotation command, and a second driver circuit connected to the other fixed contact for rotating the motor counterclockwise in response to a counterclockwise rotation command. Operation of the motor is controlled based on an output signal from the fixed contacts.
A transmission actuator, particularly a selecting transmission actuator for selecting gears, is required to select one of a plurality of gear selecting positions highly accurately. The relationship between the amount of operation of the actuator, i.e., the amount of angular displacement of the motor, and each of the gear selecting positions varies from transmission to transmission on account of dimensional variations of transmission mechanisms and actuators and wear of the transmission mechanisms in use.
With the above conventional arrangement, the movable contact and the fixed contacts are located in positions which are predetermined according to design considerations with respect to the year selecting positions which are also determined according to design considerations. Therefore, the conventional transmission actuator cannot cope with changes in the gear selecting positions of the transmission which are caused by dimensional variations of transmission mechanisms and actuators and wear of the transmission mechanisms in use.